The present invention generally relates to an anti-lock vehicle braking system (ABS), and more particularly, to such a system in which better stability of the vehicle is achieved during a braking procedure.
A vehicle braking system of the generic type, with an anti-lock system (ABS), is disclosed by German Published, Unexamined Patent Application 3,627,550. In this system, in the presence of different coefficients of friction (.mu.-split) during an ABS-control procedure to shorten the braking distance, in the case of a four-channel ABS, the braking control method for the rear wheels is switched over from "select low" to "select high". In the case of a three-channel ABS, the response/slip threshold for the beginning of control of the rear wheel brakes is raised and in the case of a vehicle with ABS and an automatically slip-limitable differential (ASD) this differential is blocked. In order to avoid provoking a sudden yawing reaction of the vehicle due to this switchover, provision is made, at least at higher vehicle speeds, to permit the rise of the brake pressure at the wheel with the higher adhesion coefficient or the raising of the slip threshold or the rise in the blocking effect of the ASD only at a particular specifiable rate of rise.
A vehicle braking system with an anti-lock system has furthermore been disclosed by German Published, Unexamined Patent Application 3,421,700, in which, to avoid high yawing moments in the case of asymmetrical coefficient of friction of the roadway and overlong braking distances, the brakes on the vehicle side having the higher coefficient of friction can be controlled as a function of the brakes on the side having the lower coefficient of friction with a time delay to produce a clocked increase of the brake pressure.
An anti-lock system for vehicles is furthermore disclosed by German Published, Unexamined Patent Application 2,518,196, in which the control can be switched over between the operating modes "select low" and "select high" as a function of various conditions, a switchover to "select high" operation being prevented for a period specified by a timing element when certain criteria are present.
It is an object of the invention to provide an anti-lock vehicle braking system of the generic type with measures for shortening the braking distance under certain conditions in such a way that even better stability of the vehicle during the braking procedure is achieved.
Compared to anti-lock vehicle braking systems of the generic type discussed above, particular advantages are obtained by preferred embodiments of the invention which includes that, at the beginning of an ABS control procedure, the driver is first given the opportunity of correcting any yawing reaction which occurs and that a higher brake-force is switched in only after this so-called stabilization phase. Any yawing reaction which occurs can then be corrected again, with the result that overall a more stable ride in combination with shortening of the braking distance is achieved.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.